Creambun - when people talk about few women orgasming from PIV, they are talking about penetration alone with no additional stimulation. AFAIK, Masters and Johnson were the first people to investigate this, precisely because porn and erotica generally portray penetrative sex that way, and it turns out that most women don't work that way. And even decades after this, popular culture (both porn and commercially produced women's written erotica whether chicklit or Harlequin or whatever) often has a proscriptive take on describing what goes on in bed, and it typically idealises the version of intercourse in which the woman comes just due to the power of the almight male cock. And unfortunately, there are women who either don't realise that you can just shove a hand down there (his, hers), use a cock ring, or whatever, or do realise, but feel inadequate about it because there's this huge propaganda about "properly sexually responsive women respond to the mighty cock and nothing else".
Yes, of course some women come with PIV alone (or do so occasionally but not regularly), but most of us need extra stimulation - but ask yourself how often you've seen this written about in fiction? Part of this is to do with the fact that writers of erotica are aiming for what one of my fellow fan-ficcers describes as "idealised realism" - you leave out the bits where your nail snags in the condom as you're putting it on, and in the resulting faff, he loses his erection (actually, I don't - I find trying to write realistic sex scenes is far more interesting). But why, in the "idealising process", does mainstream chick-lit leave out stimulation of the clitoris (other than as part of foreplay?) rather than seeking to eroticise it during PIV?
SGB - thanks for the details of that event! Sorry, the derail about rape fantasies was probably mine to start with, but I think it's an interesting one, and one that I've talked about at great length with fellow fanficcers. As you say, partly it is used as a shorthand for overwhelming passion (piggybacking on the rape myth that rapist rape because they're driven to it by short skirts... and baggy jogging bottoms, and shapeless jeans, and... well, that'll be because they're not "driven" to it at all), and also because of the confused "nice girls don't" hangover of our Christian past, whereby the only way a woman can have guilt free sex is to be "overpowered" (I read an eye-opening, but very sad blog post by a woman who'd escaped from an extreme Christian sect, bordering on cult. Not only was her adolescence "no sex", they took the "Whoever looks on a woman with lust in his heart..." verse so literally they were all expected to police their internal fantasy life - with the result that as an adult woman she found rape fantasies were the only way she could reach orgasm. She felt she'd been robbed of the ability to have a sex life she felt comfortable with, that integrated with the rest of her personality. And what was even sadder were teh BLT comments from others in similar situations - post after post saying "I thought it was just me! Thank you for telling me you feel the same. How the hell do we sort our heads out?") The other issue is one of Stockholm syndrome, either on a personal or on a cultural scale - we live surrounded by the threat of male sexual violence (that 6% who don't come with the mark of Cain on their foreheads). One way of dealing with it (not a healthy way, but cognitive dissonance rarely is) is to eroticise it: the actual rape becomes a fantasy in which eventually the rapist proves so erotic that the sex becomes consensual and he becomes tamed. Of course, it's a crock of shit, but an understandable if extremely dangerous one (dangerous in that it perpetuates rape myths).